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Pollen biostratigraphy and paleoecology of the Edmonton Formation (Maestrichtian), Alberta, Canada

1970; Elsevier BV; Volume: 7; Issue: 3 Linguagem: Inglês

10.1016/0031-0182(70)90094-5

1872-616X

Satish K. Srivastava,

Geology and Paleoclimatology Research

Nine pollen assemblage zones and three subzones, based principally on angiosperms, are recognized within 840 ft. of the Upper Cretaceous Edmonton Formation of Alberta. The two marker beds, viz., the Drumheller marine tongue and the Kneehills Tuff, divide the Edmonton Formation into lower, middle and upper members. Angiosperm pollen assemblages show three major breaks within the Edmonton Formation: at the onset of the Drumheller marine tongue; at the base of the mauve-shale containing the Kneehills Tuff; and at the top of the Nevis Coal Seam. The brackish deposition of the basal Edmonton Formation followed the regression of the Campanian Bearpaw Sea. Proximity of the sea provided humidity and a paludal environment. The prevailing subtropical humid climate supported a rain-forest-type vegetation during the deposition of the lower Edmonton member. Following the deposition of the Drumheller marine tongue, many tropical and subtropical angiosperm elements disappeared. The occurrence of temperate and warm temperate elements and an increase in the number of gymnosperm and pteridophyte species indicate an influence of a humid substropical climate with a warm temperate aspect until the deposition of the mauve-shale beds. The mauve-shale containing the Kneehills Tuff, represents lacustrine deposition with cooler climate supporting a savanna-type vegetation. Elevated sources at a distance seem to have contributed conifer pollen. The benthonitic content in the sediments may be attributed to a distant volcanic activity. Above the mauve-shale, the sediments are of flood plain origin, and the pollen flora denotes a warm temperate climate. The pollen assemblage of the Edmonton Formation is comparable with that of the Maestrichtian described from Siberia and the northern central plains of the United States of America.